Mobile operators are known to share radio communications networks in order to share costs of network operations and establishment, which are extensive, particularly in the rollout phase.
3rd Generation Partnership Project (3GPP): Technical Specification Group Services and System Aspects; Network Sharing; Architecture and functional description (Release 6) 3G TS 23.251 v6.0.0, France, June 2004, covers the details of Network Sharing. It shows how several core network operators can share one radio access network and details the impacts on the network architecture. All UE (User Equipment) entities shall also comply with other requirements for network-sharing supporting UE entities, among them PLMN selection and system information reception. Chapter 4 of the 3GPP specification describes multi-operator core network, MOCN.
An operator may select not to share its entire network but only have part of it in common with one or more other operators. For such networks and operators, prior art identifies a problem of handover related to a user communicating over a radio base station, RBS, in the shared part of the network being handed over to communicate over a base station that is not shared with one or more other operators.
FIG. 1 illustrates a handover from an MOCN radio network to an individual network of one of a plurality of partners sharing the MOCN.
To simplify the description, cells from which handover may occur to non-shared cells from shared cells and vice versa are called border cells.
3rd Generation Partnership Project (3GPP): Technical Specification Group Radio Access Network; UTRAN overall description (Release 5) 3G TS 25.401 v5.9.0, France, September 2004, describes the overall architecture of the UTRAN (Universal Terrestrial Radio Access Network), including internal interfaces and assumptions on the Iur and Iu interfaces. Iur interfaces are also referred to as radio-interfaces.
3rd Generation Partnership Project (3GPP): Technical Specification Group Radio Access Network; UTRAN Iu interface RANAP signaling (Release 5) 3G TS 25.413 v5.10.0, France, September 2004, specifies the radio network layer signaling protocol called Radio Access Network Application Part (RANAP) for the Iu interface. RANAP supports the functions of Iu interface by signaling procedures defined in this document.
The 3GPP technical specifications TS 25.401 and TS 25.413 presents a solution to the handover problem described above by specifying Shared Network Areas, SNAs, and by using shared network access control.
With a multi-operator core network, MOCN, according to 3GPP TS 23.251, the radio network will know all cells/base stations to which it is possible to hand over a call. Particularly, it will know all neighbor cells belonging to the various one or more operators, with which it shares a (sub-)network. However, the core network will only know neighbor cells belonging to the individual network.
In case a suggested border cell is not recognized by core network, handover to such a cell can be rejected. Thereby a call is guaranteed to be handed over to non-shared border cells/network of correct operator.
International Patent Applications WO02065805, WO02065806, WO02065807 & WO02065808 describe a method and system of partial support of mobility between radio access networks comprising a shared cellular radio access network. The patent applications reveal precluding user equipment from: utilizing a restricted cell, for which the subscription operator has a competing cell. Rejected utilization can be handover to, or cell/URA updating via, a restricted cell. In response to a handover attempt, the protecting control node of the auxiliary operator network obtains, from an initiating operator's network, a user equipment IMSI (International Mobile Subscriber Identity) and an identification of the target cell sought by the handover. The protecting control node uses the IMSI to determine whether the target cell is a restricted cell, and (if so) notifies the initiating operator's network that the handover is rejected.
None of the cited documents above discloses a method and system of handover in a shared radio access network environment using Iu-interface dependent neighbor-cell lists.